%\begin{center}
\begin{minipage}[t]{0.45\textwidth}

\rowheight=1.2pc
\xytree{
                &		          & \xynode{$\epsilon$} \xyconnect{1,-2} \xyconnect{1,-1} \xyconnect{1,1} \xyconnect{1,2} & \\
\xynode{$a.P_{1}$}  & \xynode{$\update{b}{Q}$}& 	        & \xynode{$b[\ ]$} \xyconnect{1,-1} \xyconnect{1,0} & \xynode{$f[\ ]$} \xyconnect{1,0}\\
	        &			  &\xynode{$c.R$} &  \xynode{$d[\ ]$} & \xynode{$g.T$}
 %\xyconnect{1,0} &		&  \\             
%\xynode{$e.S$}& 	&
}
 
\end{minipage}

%\end{center}